This invention relates to transition code processing system and more particularly to a system for generating signals representing information stored in the form of black and white coded bars for use in a data processing system.
In present-day data processing systems, the use of bar code symbols on labels or articles as a means for acquiring data at a point of sale is well-known. In reading these bar code labels, it is necessary to provide a clock pulse or other type of synchronizing signal in order that the information be properly entered from the sensing device to the utilization device. It is further necessary to provide an accurate time relationship between the movement of the sensing device with respect to the bar code symbols and the clock pulse in order for the information received to be accurately decoded. To meet these requirements, prior bar code recognition systems such as disclosed in U.S. Pat. No. 2,952,008 and U.S. Pat. No. 3,409,760 provide a separate clock or timing symbol adjacent the bar code symbol, both symbols being sensed simultaneously. Such an arrangement provides the clock pulses which bore a direct relationship to the information to be sensed. However, the requirement for controlled movement of the sensing device with respect to the bar code symbols was still important. When the movement between the sensing device and the bar code symbols was intermittent, the arrangement of prior bar code symbols and their associated sensing systems was found inadequate to functionally operate under this intermittent condition. It is therefore the primary object of this invention to provide a unique coding arrangement in which a plurality of coded symbols are capable of producing information independent of the speed of movement of the coded symbols past the sensing device while still being self-clocking. It is a further object of this invention to provide a code sensing system in which the movement of the bar code label past the sensing device is controlled by the signals generated in response to the sensing of the bar code label by the sensing device.